Syrian regime militias reach the wire threatening US-backed forces

Syrian regime forces have reached the Iraqi border for the first time in years, leading to a potentially explosive situation with nearby US-backed forces now almost encircled by the militias.

Russia's ministry of defence announced that regime militias had reached the wire on Friday, with the US-backed Syrian anti-Islamic State group fighters in al-Tanf coming under fresh pressure from hostile forces.

If expanded it opens up the possibility of Tehran directly supplying the Syrian regime with fighters by land and funneling in weapons to Hizballah forces in Lebanon.

It came after dozens of pro-regime fighters raced through Homs province on Friday afternoon to reach the border, the first time Damascus has controlled a crossing with Iraq in two years.

Pro-regime media said the fighters crossed 40km of empty desert to reach the border where they were met by Iraqi militias on the other side of the fence.

If expanded, the border position could open up a corridor between Damascus and Iraq and Iran giving the regime allies easier access to Syria.

Tehran and Baghdad have provided the regime with thousands of militants, weapons and funding in Bahsar al-Assad's fight against the rebels.

The situation could be also lead to a collision with anti-IS Syrian forces and US special forces based just 40km to the south in al-Tanf.

The base has come under pressure from regime forces advancing from another the , with the US launching air strikes on their positions to prevent the militias from advancing closer to al-Tanf.

The seizure of the border and road has also prevented the US-backed forces from launching an anticipated offensive on Deir az-Zor, with the provincial capital held by the jihadis while a regime enclave in the city is supplied by air.

The US could be concerned that plans to capture the IS-held eastern desert region of Syria could be scuppered by the latest regime advance and opens up the possibility of fresh air strikes.

Israel will also be alarmed at the potential of a direct land route opening from Iran to Hizballah in Lebanon.

A spokesperson from the US-led anti-IS coalition which has trained and supplied the Syrian fighters in al-Tanf told AFP that Washington is monitoring the situation and are ready to act.

"[There is] demonstrated hostile intent and actions of pro-regime forces near coalition and partner forces in southern Syria... [it] continues to concern us and the coalition will take appropriate measures to protect our forces," they told AFP.

"As long as pro-regime forces are oriented toward coalition and partnered forces the potential for conflict is escalated."

US forces bombed regime forces near al-Tanf for a third time this week after the militia crept into a restricted area.

A US F-15 also shot down an Shahed 129 drone in the area, after the Iranian aircraft dropped bombs on anti-IS coalition forces and allied Syrian fighters.